Officials in Tirin Kot, the provincial capital of Uruzgan province, say the bomber entered the city's police training compound while a group of officers was exercising.

Local officer Gulab Khan says officials are still trying to tally the casualties from the attack, hours after the explosion. He says the suicide bomber was wearing a police uniform when he entered the training compound. He says the attacker then detonated his bomb, killing 19 police, at the scene.

Officials say other officers are in serious condition.

A Taliban spokesman called local and foreign news outlets, soon after the attack, claiming responsibility.

The Afghan Defense Ministry later released a statement saying security forces arrested three suspected suicide bombers in Uruzgan province. The statement says the suspects were found with suicide jackets, outfitted with explosives.

Southern Afghanistan remains a stronghold of the Taliban and the center of the country's massive opium industry. United Nations officials estimate seven provinces in the south, including Uruzgan, account for 98 percent of the country's total opium poppy crop in 2008.

The opium trade is believed to be an important source of income for militants and helps fuel widespread corruption, throughout the Afghan government.

The region is mainly patrolled by Canadian, British, Dutch and Australian troops, but American commanders have recommended that some of the more than 20,000 additional U.S. troops expected in the coming months are sent to the south.

This year, the United Nations estimates smugglers exported about $3.5 billion in opium, earning Taliban militants as much as $500 million. But overall opium production is lower than in 2007, which U.N. analysts mainly attribute to low opium prices and high wheat prices. Officials say the overproduction of opium, in recent years, led to a 20 percent decrease in price this year.